1. Field of the Invention
The present invention relates to a device for a traumatic or non traumatic access to the blood circuit. The device is of the type comprising an implantable device for taking blood percutaneously and a mechanism controlling the blood flow. More particularly, the invention relates to a device for providing extra-corporeal circulation of the blood in order to compensate for poor functioning of the kidneys.
2. Description of the Prior Art
A device is already known for giving access to the blood circuit comprising a T-shaped percutaneous device formed as a single piece from a biologically compatible material, such as titanium.
In this prior art device, the lateral segments of the T each have an annular retaining flange and may be inserted directly in a blood vessel that has been previously split longitudinally and then sutured. Alternatively, the lateral segments of the T may be inserted in the middle of an artificial blood duct made from expanded polytetrafluorethylene and used to form a shunt between an artery and a vein of fairly large diameters.
The central segment of the T comprises a closure element providing sealing with respect to the lateral segments. The central segment is formed with a transverse circular dividing wall made from silicon elastomer. The transverse circular dividing wall has two slits formed along the same diameter, spaced from the edge of the wall, and separated by a solid central part. A needle or cannula device connected to the blood cleansing system may be introduced into each of the slits. The centering of the needle or cannula device with respect to each slits is obtained by two semispherical depressions centered about the slits.
The needle or cannula devices are held clamped by means of an elastomer toroidal clamping ring inserted in a circular groove formed in the thickness of the transverse circular dividing wall. The clamping ring provides the required functional sealing.
The transverse circular dividing wall is held in position by means of a transverse compression plate formed as a single piece with a tubular compression ring. The tubular compression ring is force fitted in the cavity of the central segment of the T and is held in position by means of two projections which project outwardly from the upper edge of the transverse compression plate. The two projections snap fit into a circular groove formed in the vicinity of the corresponding edge of the central segment of the T.
The transverse compression plate has two orifices corresponding to the two previously mentioned slits. The transverse compression plate separates an upper chamber from a lower chamber. In the lower chamber, the upper part of the transverse circular dividing wall is imprisoned by force. An eccentric alignment stud juts out between the slits and the orifices. The eccentric alignment stud projects from the lower surface of the transverse compression plate and is housed in a corresponding cavity in the transverse circular dividing wall.
The prior art percutaneous device may have a pyrolytic carbon coating for increasing its biocompatibility. It may further have, except on the upper part of the central segment of the T, a coating of a porous material such as polyethylene terephtalate or porous titanium. The porous material forms a supporting structure which may be colonized by tissue growth.
The tubular compression ring may be made from a biocompatible metal. Alternatively, the tubular compression ring may be made by injection molding of a plastic material such as polycarbonate or polysulfone, possibly reinforced with a glass, carbon, or mineral charge.
Insertion and extraction of the assembly consisting of the transverse circular dividing wall and the tubular compression ring is achieved by means of tools specially designed for this purpose.
A second prior art device is known for giving access to the blood circuit. The second prior art device may also be connected to a blood vessel directly or through an arterial-venous shunt.
The second prior art device comprises a percutaneous device formed by a conical blood flow duct made from a biocompatible material. The conical blood flow duct is non-porous- and non-biodegradable, and it may be made from pyrolytic carbon deposited on a graphite substrate or from vitreous carbon the external surface of which has a smooth appearance. The conical blood flow duct comprises at the distal end a first perforated fixing collar and, in the intermediate part, a second perforated fixing collar for biological anchorage through invasion of the perforations by tissue growth.
The second prior art also comprises a closure element, solid and also conical, for the conical blood flow duct. The closure element ends in a non-conical proximal part improving the sealing.
The percutaneous device cooperates with an atraumatic mechanism for controlling the blood flow through a rod actuated from the outside which is screwed into the closure element after passing through an orifice formed in a closure chamber of the conical flow duct. The closure chamber is in communication with a blood treatment device through a single tube. The blood is alternately drawn through the single tube for treatment, then returned to the body. Alternatively, the blood may be circulated by means of two tubes, the first of which is intended for drawing off the blood and the second of which is intended for returning the blood simultaneously to the body. The control mechanism also cooperates with a ring for fixing the closure chamber against a flange of the conical blood flow duct.
The conical blood flow duct comprises at least a partial coating disposed between the first and second perforated fixing collars. The coating is made from a vascular grafting material such as polyethylene terephtalate. Additionally, the coating comprises a partial microporous coating impermeable to blood, and thus minimizing the blood loss, which is applied in correspondence with the first perforated fixing collar and is made from polytetrafluorethylene.
The conical closure element may also have two channels separated by a longitudinal central dividing wall connected to its base. The base closes the flow duct in the rest condition.
The two channels each communicate, at the lower part, with a transverse orifice formed in the vicinity of the base of the conical closure element. Additionally, the two channels each communicate, in the upper part, with a tubular flow chamber connected to a blood treatment device.
In this case, using an appropriate control tool, the conical closure element, connected to the tubular flow chambers, may be lowered and the base of the conical closure element with the transverse orifices plunged in the blood flow, thus establishing the desired extracorporeal circulation. By actuating the control tool in the opposite direction, the conical closure element with the tubular flow chambers may be raised, which causes closure of the transverse orifices and stops the extracorporeal circulation.
In the rest condition the base closes the flow duct, and the conical closure element has a certain functional play with respect to the walls of the flow duct. That play is just sufficient to allow it to be lowered into the open position, so that the transverse orifices are again exposed to the blood flow.
The prior art has drawbacks, more especially:
in so far as the percutaneous device is concerned: PA1 in so far as the blood flow control mechanism is concerned, it comprises numerous parts, which are often difficult to clean, resulting in a greater risk of clotting or insufficient asepsis; and PA1 in so far as the access device to the blood circuit as a whole is concerned, it requires the use of numerous accessory tools, which complicates the use of the access device. PA1 the biological anchorage of the percutaneous device by tissue growth is more intimate, which ensures PA1 sealing and cleaning of the percutaneous device are more reliable; PA1 actuation of the control mechanism does not require any tools, which makes it particularly simple and reliable; and PA1 the parts of the control mechanism are reduced to a minimum and their shape is such that cleaning is very easy and reliable, which eliminates the risk of stopping the blood flow by clotting or insufficient asepsis. PA1 an implantable device having a tubular segment for access to a blood vessel and projecting slightly from the cutaneous surface; PA1 a control device for controlling the blood flow through the closure element, the control device having a proximal part and a distal part; and PA1 a cover for closing the tubular segment giving access to the blood.
the reliability and cleaning are problematical; PA2 the porous coating which may be colonized by tissue growth has, because of the materials used up to present and with respect to the organic tissues, biological affinity which is far from being total, which also prevents in this case a truly intimate anchorage, so PA2 the resistance to accidental tearing forces exerted at the junction of the skin is low, which creates "marsupialization" of the skin with risks of infection; PA2 a higher resistance to accidental tearing forces exerted at the junction of the skin, and PA2 a more efficient barrier against the penetration of bacteria at the seat of the implantation, thus eliminating risks of infection;